feat!: replace output_text property with getResponseOutputText helper (#48)

Adds a simple helper function to extract aggregated text output from
ResponseObject instances.

This **replaces** the automatic `output_text` property approach from PR
#42 with an explicit helper function, providing a cleaner API without
prototype patching or side-effectful imports.

## Changes

- **Removes** `src/lib/init.ts` (automatic property patching)
- **Adds** `getResponseOutputText()` helper function
- Works for both streaming and non-streaming responses

## Usage

### Streaming responses
```typescript
import { getResponseOutputText } from 'llama-stack-client';

const stream = await client.responses.create({ stream: true, ... });
for await (const chunk of stream) {
  if (chunk.type === 'response.completed') {
    const text = getResponseOutputText(chunk.response);
    console.log(text);
  }
}
```

### Non-streaming responses
```typescript
import { getResponseOutputText } from 'llama-stack-client';

const response = await client.responses.create({ stream: false, ... });
const text = getResponseOutputText(response);
```

This provides a clean, explicit API for accessing aggregated text from
responses without relying on magic property injection.

Author: ashwinb

src/index.ts

@@ -151,9 +151,6 @@ import {
   VectorStoresOpenAICursorPage,
 } from './resources/vector-stores/vector-stores';
 
-// MANUAL: Auto-install response helpers (preserve across regeneration)
-import './lib/init';
-
 export interface ClientOptions {
   /**
    * Defaults to process.env['LLAMA_STACK_CLIENT_API_KEY'].
@@ -573,6 +570,7 @@ export declare namespace LlamaStackClient {
   export type SystemMessage = API.SystemMessage;
 }
 
+export { getResponseOutputText } from './lib/response-helpers';
 export { toFile, fileFromPath } from './uploads';
 export {
   LlamaStackClientError,

src/lib/init.ts

@@ -0,0 +1,60 @@
+// Copyright (c) Meta Platforms, Inc. and affiliates.
+// All rights reserved.
+//
+// This source code is licensed under the terms described in the LICENSE file in
+// the root directory of this source tree.
+
+/**
+ * Helper utilities for working with response objects.
+ */
+
+import type { ResponseObject } from '../resources/responses/responses';
+
+/**
+ * Extracts aggregated text output from a ResponseObject.
+ * This concatenates all `output_text` entries from the response's output array.
+ *
+ * Useful for streaming responses where you want to get the final text from chunk.response:
+ *
+ * @example
+ * ```ts
+ * const stream = await client.responses.create({ stream: true, ... });
+ * for await (const chunk of stream) {
+ *   if (chunk.type === 'response.completed') {
+ *     const text = getResponseOutputText(chunk.response);
+ *     console.log(text);
+ *   }
+ * }
+ * ```
+ */
+export function getResponseOutputText(response: ResponseObject): string {
+  const pieces: string[] = [];
+
+  for (const output of response.output ?? []) {
+    if (!output || output.type !== 'message') {
+      continue;
+    }
+
+    const content = output.content;
+    if (typeof content === 'string') {
+      pieces.push(content);
+      continue;
+    }
+
+    if (!Array.isArray(content)) {
+      continue;
+    }
+
+    for (const item of content) {
+      if (typeof item === 'string') {
+        pieces.push(item);
+        continue;
+      }
+      if (item && item.type === 'output_text' && 'text' in item && typeof item.text === 'string') {
+        pieces.push(item.text);
+      }
+    }
+  }
+
+  return pieces.join('');
+}